[llvm] VT/test: pre-commit tests to enable samesign optz (PR #120257)

[Florian Hahn via llvm-commits]

https://github.com/fhahn approved this pull request.

LGTM, thanks! Might be good to add some variants of the `incr` tests without `nuw/nsw` as well?

https://github.com/llvm/llvm-project/pull/120257